resource/aws_emr_cluster: Add core_instance_fleet and master_instance…

…_fleet configuration blocks (#14788)

Output from acceptance testing (failure unrelated):

```
--- FAIL: TestAccAWSEMRCluster_Ec2Attributes_DefaultManagedSecurityGroups (761.58s)
--- PASS: TestAccAWSEMRCluster_additionalInfo (389.66s)
--- PASS: TestAccAWSEMRCluster_basic (421.31s)
--- PASS: TestAccAWSEMRCluster_bootstrap_ordering (1315.25s)
--- PASS: TestAccAWSEMRCluster_configurationsJson (488.41s)
--- PASS: TestAccAWSEMRCluster_CoreInstanceGroup_AutoscalingPolicy (530.87s)
--- PASS: TestAccAWSEMRCluster_CoreInstanceGroup_BidPrice (1073.94s)
--- PASS: TestAccAWSEMRCluster_CoreInstanceGroup_InstanceCount (578.27s)
--- PASS: TestAccAWSEMRCluster_CoreInstanceGroup_InstanceType (822.02s)
--- PASS: TestAccAWSEMRCluster_CoreInstanceGroup_Name (885.45s)
--- PASS: TestAccAWSEMRCluster_custom_ami_id (546.87s)
--- PASS: TestAccAWSEMRCluster_disappears (443.96s)
--- PASS: TestAccAWSEMRCluster_ebs_config (555.62s)
--- PASS: TestAccAWSEMRCluster_instance_fleet (454.47s)
--- PASS: TestAccAWSEMRCluster_instance_fleet_master_only (429.68s)
--- PASS: TestAccAWSEMRCluster_keepJob (390.32s)
--- PASS: TestAccAWSEMRCluster_Kerberos_ClusterDedicatedKdc (520.68s)
--- PASS: TestAccAWSEMRCluster_MasterInstanceGroup_BidPrice (949.21s)
--- PASS: TestAccAWSEMRCluster_MasterInstanceGroup_InstanceCount (1074.24s)
--- PASS: TestAccAWSEMRCluster_MasterInstanceGroup_InstanceType (976.43s)
--- PASS: TestAccAWSEMRCluster_MasterInstanceGroup_Name (930.00s)
--- PASS: TestAccAWSEMRCluster_root_volume_size (780.90s)
--- PASS: TestAccAWSEMRCluster_s3Logging (528.25s)
--- PASS: TestAccAWSEMRCluster_security_config (687.55s)
--- PASS: TestAccAWSEMRCluster_Step_Basic (493.95s)
--- PASS: TestAccAWSEMRCluster_step_concurrency_level (543.97s)
--- PASS: TestAccAWSEMRCluster_Step_ConfigMode (896.25s)
--- PASS: TestAccAWSEMRCluster_Step_Multiple (493.67s)
--- PASS: TestAccAWSEMRCluster_tags (820.00s)
--- PASS: TestAccAWSEMRCluster_terminationProtected (614.80s)
--- PASS: TestAccAWSEMRCluster_visibleToAllUsers (946.47s)
```